1. Field of the Invention
The present invention relates to a controller of an internal combustion engine having a function of sensing a time necessary for a unit angle of a crankshaft of the engine to rotate based on an output of a crank angle sensor sensing sensed portions formed for respective unit angles at equal intervals on a rotating body rotating in synchronization with rotation of the crankshaft.
2. Description of Related Art
It is common knowledge to sense multiple tooth portions (sensed portions) formed at equal intervals on a rotor provided on a crankshaft of an in-vehicle internal combustion engine with a crank angle sensor in order to calculate a time necessary for the crankshaft to rotate. A magnetic flux between the crank angle sensor and the rotor changes regularly because a positional relationship between the crank angle sensor, which is located near the rotor, and the tooth portions of the rotor changes regularly. Paying attention to this fact, the rotation of the tooth portions of the rotor is sensed based on the regular flux change.
In order to sense a reference position of the rotation angle of the crankshaft, a toothless portion is usually provided on the rotor by irregularly changing the disposal of the above-described tooth portions. Accordingly, the regularity of the flux change is disturbed if the crank angle sensor approaches to the toothless portion while the magnetic flux between the crank angle sensor and the rotor changes regularly with the rotation of the crankshaft. The reference position of the rotation angle of the crankshaft can be sensed based on disturbance of the regularity of the flux change.
However, since the regularity of the flux change is disturbed near the toothless portion, the rotation angle cannot be sensed with high accuracy. Control based on information with high accuracy about the rotation angle of the crankshaft cannot be performed if the engine is controlled based on the sensing value of the crank angle sensor. As a result, controllability deteriorates and there is a possibility that exhaust characteristics and drivability are deteriorated. For example, JP-A-2005-48644 describes a controller that controls an internal combustion engine based on a rotation angle of a crankshaft.
The problem of the deterioration of the controllability of the engine is not limited to the angle range having the toothless portion. This problem is common to a range where the time necessary for the rotation cannot be sensed appropriately, such as, a range where the time necessary for the rotation of the crankshaft cannot be sensed temporarily.